Abstract
Impaired follicular development associated with autoimmune ovarian disease (AOD), is a typical side effect of ZP3 vaccine-induced subfertility and contributes to the fertility decline, but the mechanism is unknown. In this study, a AOD model was established with recombinant mouse zona pellucida 3 (mZP3) protein in the BALB/c mice, and co-administrated with 0.5 mg/kg antioxidant stress drug sodium selenite (SS), whereas intraperitoneal injection was used and the relationships among oxidant stress (OS), follicle loss and fertility were evaluated. Here we demonstrated that ZP3 vaccination elicited high antibody titers and correlated with reductions of ovarian follicle numbers in both fertile and infertile mice, whereby magnitudes of both factors were negatively correlated with litter size. Moreover, increased OS in ovaries of mZP3-immunized mice was related to high levels of reactive oxygen species (ROS) and malondialdehyde (MDA), and is accompanied by a decrease in the total antioxidant capacity (TAC) of ovaries. Meanwhile, activation of caspase-3 and caspase-9 along with increased Bax and decreased Bcl-2 levels were observed, indicating the ongoing apoptosis of ovarian cells. Notably, inhibition of OS with SS reduced ovarian ROS and apoptosis levels, which was consisted with restoration of follicle numbers. More importantly, SS treatment when co-administered concurrently with mZP3 immunization led to significantly improved fertility (P < 0.05) and the average litter size of the mZP3-vaccinated SS-treated group increased by ~29.2% as compared with that of the vaccinated but untreated group. In conclusion, infertility caused by ZP3 vaccination was mechanistically associated with ovarian OS which triggered depletion of ovarian follicles.
Highlights
Zona pellucida 3 (ZP3), the primary oocyte receptor for sperm recognition, has been recognized as a potential candidate for use as birth controlling target in mammalian species by immunizing using ZP3 vaccination [1,2,3]
Statistical analysis of data obtained in this study revealed no differences in fertility rates among the three groups mouse zona pellucida 3 (mZP3)+sodium selenite (SS), mZP3+Saline and glutathione S-transferase (GST)+Saline, which were 90% (9/10), 70% (7/10) and 100% (10/10), respectively
All mice were subjected to mating on day 36 after the first immunization. bPercentage of fertile mice were calculated by the fertile numbers divided by the total mated females in each group. cTotal number of pups of each group were counted 21∼27 days after animals mating. dMean litter size of mice were calculated by the total pups divided by the total mated females in each group. eSignificant differences (*P < 0.05 and **P < 0.01) are presented between immunized groups and negative controls (GST+Saline)
Summary
Zona pellucida 3 (ZP3), the primary oocyte receptor for sperm recognition, has been recognized as a potential candidate for use as birth controlling target in mammalian species by immunizing using ZP3 vaccination [1,2,3]. ZP3 immunization is associated with AOD and typically induces symptoms of premature ovarian failure (POF) [4, 5], greatly limiting its applicability as a contraceptive [5]. Individual differences are observed among experimental subjects, ZP3-induced ovarian inflammation is closely associated with ovarian dysfunction and fertility, with severe inflammation often accompanied with fewer follicles and smaller litter sizes [4, 8]. Vaccination-induced ovarian dysfunction is characterized by follicular atresia, vacuolation, luteinization and other signs that may be responsible for the reduction or total elimination of follicles and subsequent infertility [9, 10]. Ovarian inflammation may be related to these pathological effects despite its role in fertility decline remains unclear
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